1. Field of the Invention
The present invention relates to an inkjet printer, and more particularly a high-speed inkjet printer capable of reliably forming high-quality images.
2. Related Art
Line-scan inkjet printers are a type of high-speed inkjet printer capable of printing on a continuous recording sheet at high speed, and include an elongated inkjet recording head formed with rows of nozzles for ejecting ink droplets. The head is arranged in confrontation with the surface of the recording sheet across the entire width of the recording sheet. The head selectively ejects ink droplets from the nozzles based on a recording signal and impinges the droplets on desired positions across the width of the recording sheet. At the same time, the recording sheet is transported rapidly in its lengthwise direction, which serves as a main scanning operation, so that images can be recorded at any place on the recording sheet.
Various types of line-scan inkjet printers have been proposed, such as printers that use a continuous inkjet type recording head and printers that use a drop-on-demand type recording head. Although drop-on-demand type line-scan inkjet printers have a slower printing speed than do continuous inkjet type line-scan inkjet printers, they have an extremely simple ink system and so are well suited for a general-purpose high-speed printer.
A recording head of a drop-on-demand type line-scan inkjet printer disclosed in Japanese Patent-Application Publication (Kokai) No. 2001-47622 includes nozzle elements that eject ink droplets through corresponding nozzles when a driving voltage is applied to corresponding piezoelectric elements or heat-generating elements. A charge/deflect electrode is provided along a nozzle row for deflecting ejected ink droplets so that a plurality of ink droplets ejected from adjacent nozzles impinge on the same pixel position. With this configuration, a complete image can be obtained without missing any information even if one or more of the nozzle elements become defective. Further, uneven color density undesirably appearing on obtained images due to unevenness in characteristics among the nozzle elements can be prevented. Accordingly, highly-reliable drop-on-demand line-scan inkjet recording devices are provided.
There is also proposed to eject refresh ink droplets that do not contribute to forming dots on a recording sheet, in order to prevent ink clinging around nozzles from drying and getting dense since high-viscosity ink clinging around the nozzles prevents proper ink ejection. The ejected refresh ink droplets are deflected and collected by an ink collection member without impinging on the recording medium.
Here, FIGS. 1(a) and 1(b) show a configuration of a conceivable deflecting device, wherein ejected refresh ink droplets 142 are deflected by an angled electric field 85 so as to impinge on ink reception absorption bodies 27 embedded in nozzle electrodes 221 after traveled along U-turn paths 93. The nozzle electrodes 221 are disposed for every one of nozzle rows 121, that is, the nozzle electrodes 221 are provided in one-to-one correspondence with the nozzle rows 121. Accordingly, when a recording head has a large number of nozzle rows 121 arranged at a narrow pitch where a gap between adjacent two nozzle rows 121 is small, then electrode windows 22 provided for every nozzle rows 121 cannot have a sufficient width. In this configuration, only an insufficient space is provided between a nozzle row 121 and a nozzle electrode 221 for an adjacent nozzle row 121. Accordingly, the angled electric field 85 can have only a small field element perpendicular to an ink ejection direction and may deflect the refresh ink droplets 142 only by an insufficient amount.
That is, in FIG. 2, where there is a great difference between space SB, which is a distance between a nozzle row 121A and a nozzle electrode 221B for an adjacent nozzle row 121B, and a space SA which is a distance between the nozzle row 121A and a corresponding nozzle electrode 221A, then, a stronger electric field is generated. On the other hand, when there is only a small difference between the space SB and the space SA, then there is only generated a weak electric field. This is because an electric field generated by the nozzle electrode 221B weakens the electric field generated by the nozzle electrode 221 A.
Moreover, in the configuration of FIGS. 1(a) and 1(b), the nozzle electrodes 221 can only have a narrow width, so that ink reception absorption bodies 27 embedded in the bottom surface of the nozzle electrodes 221 only have a narrow width also. Accordingly, if the refresh ink droplet 142 that has been deflected to fly along the U-turn path 93 travels a relatively long distance, then the refresh ink droplet 142 does not impinge on the ink reception absorption body 27, that is, the ink reception absorption body 27 fails to collect the refresh ink droplet 142.
In view of the foregoing, it is an object of the present invention to overcome the above problems and also to provide a deflection device that effectively deflects refresh ink droplets so that the deflected refresh ink droplets are reliably collected by an ink collection member without reaching a recording medium.
In order to achieve the above and other objects, according to the present invention, there is provided an inkjet head including a body formed with a plurality of nozzle rows each including a plurality of nozzles through which ink droplets are ejected, and a plurality of electrodes provided for generating a deflecting field that deflects the ink droplets ejected from the nozzles. One electrode is provided for every two nozzle rows. Each electrode is provided between the corresponding adjacent two nozzle rows.
There is also provided an inkjet head including a body formed with a plurality of nozzle rows each including a plurality of nozzles through which ink droplets are ejected, and a plurality of reception bodies for receiving the ink droplets ejected from the nozzles. One reception body is provided for every two nozzle rows. Each reception body is provided between the corresponding adjacent two nozzle rows and receives the ink droplets ejected from the nozzles of the corresponding two adjacent nozzle rows.
Further, there is provided an inkjet recording device including an inkjet head formed with a plurality of nozzle rows each including a plurality of nozzles through which ink droplets are ejected, and a plurality of electrodes for generating a deflecting field that deflects the ink droplets ejected from the nozzles. One electrode is provided for every two nozzle rows. Each electrode is provided between the corresponding adjacent two nozzle rows.